Cavolinia tridentata (Niebuhr, 1775) forma atlantica Van der Spoel, 1974

Overview

This is a large shelled pteropod, 1.6 cm long. It has a flat dorsal side with moderately developed ribs. There are no keels along the lateral sides. The caudal spine is short and straight. The ventral side is moderately vaulted. The shell sculpture consists of faint growth lines and a very faint transverse striation. Micro-zooplankton and phytoplankton are its food, it is a mucus feeder. It lives at moderate depths in the S-Atlantic Ocean (Cavolinia t. atlantica dorsal, Cavolinia t. atlantica lateral).

Taxonomic Description

The hyaline shell has a moderately vaulted dorsal surface (Cavolinia t. atlantica outline). The central rib, on the dorsal side, is well developed, the lateral ribs are less developed. A well developed arch-shaped rib is found at the base of the dorsal lip. The lateral sides do not have keels. The lateral spine points are directed slightly caudally, the caudal spine is short and straight. The shell margin, between caudal and lateral spines, is concave with a more or less straight horizontal portion. The ventral side is moderately vaulted (Cavolinia t. atlantica early adult). The aperture is triangular (Cavolinia t. atlantica). The dorsal aperture lip is rounded or it may have a small additional part with a short straight section, about 3 mm long. The growth lines on the shell are faint and the transverse striation is poorly developed. A light-brown hue nearly covers the whole shell.
The shell length varies between 11.5 and 16.0 mm, the width varies between 8.0 and 10.5 mm, with averages of 15.2 and 9.9 mm respectively.

Juveniles

A special description is not available.

Reproduction

Cavolinia tridentata forma atlantica is a protandric hermaphrodite.

Ecology

Cavolinia tridentata forma atlantica is phytophagous and epipelagic.

Distribution

Cavolinia tridentata forma atlantica occurs in the S-Atlantic between 5°N and 40°S, see the Cavolinia t. atlantica map.

Types

Cavolinia tridentata forma atlantica Van der Spoel, 1974: 106, fig. 4c, 6.
The holotype (U.S.N.M. 123920) (fig. 4c) and one paratype (U.S.N.M. 703765) is stored dry in the USNM, one paratype is stored dry in the ZMAN.
Type locality: St. Helena, coll. Turton.

Kingdom Animalia
Phylum Mollusca
Class Gastropoda
Subclass Euthyneura
Order Thecosomata
Suborder Euthecosomata
Family Cavoliniidae
Subfamily Cavoliniinae
Genus Cavolinia
Species Cavolinia tridentata
Forma atlantica

Status in World Register of Marine Species

Not included in WoRMS database

Scientific synonyms and common names

Cavolinia tridentata (Niebuhr, 1775) forma atlantica Van der Spoel, 1974

Synonyms

Cavolinia tridentata forma atlantica n. forma Van der Spoel, 1974: 106

This forma has usually been named Cavolinia tridentata by previous authors.

Magaldi, N. H., 1977a. Moluscos holoplanctonicos del Atlantico suboccidental. III. Heteropods y pteropods de aguas superficiales Brasilenas y Uruguayas. Com. Soc. Malac. Urug. 4 (33): 295-325.

Rampal, J., 1975. Les thécosomes (mollusques pélagiques). Systématique et évolution écologie et biogéographie méditerranéennes. Aix-Marseille (Thesis Univ. Provence CNRS AO 11932): 1-485, 15 tabs, 99 figs.

Spoel, S. van der and Boltovskoy, D., 1981. Pteropoda. In: Boltovskoy, D. (ed.). Atlas del zooplancton del Atlantico Sudoccidental. Publ. INIDEP Argentina: 493-512.

Spoel, S. van der and Heyman, R. P., 1983. A comparative atlas of zooplankton. Biological patterns in the oceans. Bunge, Utrecht; Springer Verl., Berlin: 1-186.

Spoel, S. van der, Boltovskoy, D. and Jankivich, S. S., 1981. Classification y distribucion. In: Boltovskoy, D. (ed.). Atlas del zooplancton del Atlantico Sudoccidental. Publ. INIDEP Argentina: 512-524.

Spoel, S. van der, 1974. Geographic variation in Cavolinia tridentata (Mollusca, Pteropoda). Bijdr. Dierk. 44 (1): 100-112.

Spoel, S. van der, 1976c. Pseudothecosomata, Gymnosomata and Heteropoda. Bohn, Scheltema & Holkema, Utrecht. 484 pp. 246 figs.

Spoel, S. van der, 1981a. Descripcion de los conchas embrionarias de Cavoliniidae. In: Boltovskoy, D. (ed.). Atlas del zooplancton del Atlantico Sudoccidental. Publ. INIDEP Argentina: 525-531.

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